Methods for detecting failure states in a medicine delivery device

ABSTRACT

A fluid medicament delivery device includes a patient attachment unit, containing the fluid medicament, and an indicator unit adapted to be detachably coupled to the patient attachment unit. A method for monitoring the fluid medicament includes independently setting a flow rate of a fluid medicament with the patient attachment unit. A pressure and/or a flow rate of the fluid medicament is sensed with a sensor located in a separate indicator unit in a sensing mode. A status of the fluid medicament delivery device is determined based at least in part on the pressure and/or the flow rate.

FIELD OF THE INVENTION

This invention relates generally to medicament delivery devices and,more specifically, to medicament infusion devices that utilize areusable indicator unit and a disposable medicament delivery unit.

BACKGROUND

Medicament infusion devices are utilized to deliver liquid fluidmedicine to patients. For example, insulin infusion devices are oftenused by persons with diabetes to maintain adequate insulin levelsthroughout the day or to increase insulin levels during mealtime. Theseinsulin infusion devices can replace the syringe-based injections commonamong those with diabetes.

Insulin infusion devices are available in several forms, and includeseveral common components. Generally, an infusion device includes ahousing that may be worn on a patient's clothing (a belt, for example)or on the patient himself, and that contains a number of mechanical andelectrical components. A reservoir holds the insulin and anelectro-mechanical pump mechanism (various types are used) delivers theinsulin as needed to the patient. Battery-powered electronics controlthe pump and ensure that the device is operating properly. Varioussensors communicate with the electronics and other components to detectocclusions, sound alarms, measure remaining insulin capacity, etc.

While these devices are useful, they do suffer from severalshortcomings. First, the high expense of the devices makes themaccessible to fewer people than the diabetic population members who maybenefit from their use. Second, failure or malfunction of one componentrequires repair or replacement of the entire device, a costly scenario.For example, if the pump fails, often the entire unit (including theproperly functioning—and expensive—electronics) must be replaced. Third,over time the device gets dirty due to repeated uses, which requiresperiodic cleaning and may cause a failure condition at a later date.Fourth, the complexity of the devices requires significant battery powerto operate pumps, monitor sensors, and send alerts and notifications toa patient. Power and electronic requirements are often so significant asto excessively require large batteries, thus increasing the physicalsize and cost of the device.

SUMMARY OF THE INVENTION

What is needed, then, is a medicament infusion device that utilizeslow-cost components, some of which may be replaced periodically afteruse, without having to dispose of other expensive, but operational,components in the device.

In general, in one aspect, embodiments of the invention feature a systemfor monitoring a fluid medicament delivery device that includes apatient attachment unit and an indicator unit. The patient attachmentunit independently sets a flow rate of a fluid medicament containedtherein. The indicator unit monitors a parameter of interest of thefluid medicament is adapted to be detachably coupled to the patientattachment unit, and includes a sensing module, a status determinationmodule, and a notification module. The sensing module for receives asignal, indicating at least one of a pressure and a flow rate of thefluid medicament, from a sensor located in the patient attachment unit.The status determination module determines a status of the fluidmedicament delivery device based at least in part on the receivedsignal. The notification module notifies a patient of the status.

The patient attachment unit may be adapted to be attached to a skinsurface of the patient, and the sensing module may include a MEMSsensor. An initialization module may perform a system initializationtest (e.g., a battery status test). A result of the battery status testmay be based at least in part on a volume of the fluid medicament and/oran amount time. Based on the result, the notification module may notifythe patient.

The status may include a fault condition (e.g., an out-of-fluidcondition and a time limit condition) based at least in part on a volumeof the fluid medicament, a pressure of the fluid medicament, a flow rateof the fluid medicament, a hardware fault, and/or an amount of time. Thestatus may include a system-OK condition, an occlusion condition, and/ora low-reservoir volume condition. The patient attachment unit mayinclude a variable-volume chamber in which a fluid is at least partiallycontained. The variable-volume chamber unit may include a flexiblemember, and a movement of the flexible member may be sensed by thesensing module. The notification module may further include an alarm(e.g., an audible alarm, a visual alarm, and/or a tactile alarm).

In general, in another aspect, embodiments of the invention feature amethod for monitoring a fluid medicament delivery device. The deviceincludes a patient attachment unit (which includes a reservoir forreceiving the fluid medicament therein) and an indicator unit (which isadapted to be detachably coupled to the patient attachment unit). A flowrate of a fluid medicament in independently set with a patientattachment unit. During a sensing mode, a pressure and/or a flow rate ofthe fluid medicament are sensed with a sensor located in a separateindicator unit. A status of the fluid medicament delivery device isdetermined based at least in part on a result the pressure and/or theflow rate. The patient is notified of the status.

The patient attachment unit may be adapted to be attached to a skinsurface of the patient. The sensing mode may be initiated upon receiptof an interrupt request, which may be triggered by an expiration of asample timer and/or an actuation of a button. An ambient air pressuremay be sensed, and the ambient air pressure may be compared to the fluidpressure. Forensic data may be stored in a nonvolatile memory.

A system initialization test (e.g., a battery power test and/ordetecting a hardware fault) may be conducted, and the patient may benotified in the event of low battery power. Notifying the patient (e.g.,sending an audible notification comprising at least two tones) mayinclude sending a discreet notification followed by an overtnotification, and the overt notification may be cancelled base at leastin part on a request from the patient.

In another aspect, the invention relates to a fluid medicament deliverydevice having a patient attachment unit that includes a housing and afluid channel located therein, such that at least a portion of the fluidchannel has a flexible member substantially coterminous with thehousing. The fluid medicament delivery device includes a separateindicator unit adapted to be detachably coupled to the housing of thepatient attachment unit. The indicator unit includes a first sendingelement for contacting the flexible member when the indicator unit iscoupled to the housing, such that the first sensing element senses aflexure of the flexible member. In an embodiment of the foregoingaspect, the indicator unit also includes a second sending element forsending a pressure external to the housing. In another embodiment, thepressure external to the housing includes an ambient pressure.

In an embodiment of the above aspect, the first sensing element includesa pressure sensor. In another embodiment, the first sensing element alsoincludes at least one of a fluid and a gel adapted to contact theflexible member, such that the flexure of the flexible member istransmitted by the at least one of the fluid and the gel to the pressuresensor. In yet another embodiment, the separate indicator unit defines awell for containing at least one of the liquid and the gel. In stillanother embodiment, the separate indicator unit includes a raised lipsurrounding the well, such that the raised lip is disposed above aproximate portion of the separate indicator unit. In another embodiment,the raised lip is adapted to contact the housing of the patientattachment unit.

In another embodiment of the above aspect, the second sensing elementincludes a pressure sensor adapted to sense the pressure external to thehousing, and at least one of a fluid and a gel adapted to transmit thepressure external to the housing to the pressure sensor. In anembodiment, the housing has a hermetically-sealed housing defining aninterior space and including at least one substantially flexible housingportion. The substantially flexible housing portion is adapted fortransmitting the pressure external to the housing to the interior space.In still another embodiment, the substantially flexible housing portionis located on a portion of the patient attachment unit facing theseparate indicator unit and the second sensing element is located on aportion of the separate indicator unit facing the patient attachmentunit, when the patient attachment unit is coupled to the separateindicator unit.

In yet another embodiment of the foregoing aspect, the patientattachment unit is adapted for adhesion to a skin surface of a patient.In an embodiment, the fluid medicament delivery device also includes aprocessor adapted for interpreting a signal from a pressure sensor, suchthat the signal is sent to the processor based at least in part of theflexure of the flexible member.

In another aspect, the invention relates to a method of monitoringpressure within a fluid channel of a fluid medicament delivery device,the method including measuring an actual pressure of a fluid within thefluid channel, comparing the actual pressure to a pressure rangeincluding a maximum pressure and a minimum pressure, and sending anotification when the actual pressure is outside of the pressure range.In an embodiment, the method also includes measuring a pressure externalto fluid medicament delivery device.

In an embodiment of the above aspect, the method of monitoring pressurewithin a fluid channel of a fluid medicament delivery device alsoincludes modifying the actual pressure base on the external pressure toobtain a corrected pressure, and comparing the corrected pressure to thepressure range. In another embodiment, the method also includesmodifying the maximum pressure and a minimum pressure of the pressurerange based on the external pressure to obtain a corrected pressurerange, and comparing the corrected pressure range to the actualpressure. In still another embodiment, when the actual pressure exceedsthe maximum pressure, the notification includes at least one of adownstream occlusion notification and a near-empty reservoirnotification. In yet another embodiment, when the actual pressure isless than the minimum pressure, the notification includes at least oneof an upstream occlusion notification and an empty reservoirnotification.

In another aspect, the invention relates to a method of manufacturing apressure sensing element, the method including securing a pressuresensor to a base, securing a template defining a well therein to thebase, such that the pressure sensor is located in a bottom portion ofthe well. The method includes filling at least partially the well with agel having a substantially liquid state, so the well includes a filledportion and an unfilled portion, and the filled portion and the unfilledportion are characterized by a presence or and absence of gel. Themethod includes solidifying the gel in the filled portion to asubstantially gelled state, and filling the unfilled portion with a gelhaving a substantially liquid state.

These and other objects, along with advantages and features of theembodiments of the present invention herein disclosed, will become moreapparent through reference to the following description, theaccompanying drawings, and the claims. Furthermore, it is to beunderstood that the features of the various embodiments described hereinare not mutually exclusive and can exist in various combinations andpermutations

BRIEF DESCRIPTION OF THE FIGURES

Other features and advantages of the present invention, as well as theinvention itself, can be more fully understood from the followingdescription of the various embodiments, when read together with theaccompanying drawings, in which:

FIG. 1 is a schematic top view of a fluid medicament delivery device inaccordance with one embodiment of the invention;

FIG. 2 is a schematic side view of the fluid medicament delivery deviceof FIG. 1;

FIG. 3 is a schematic diagram of an exemplary infusion devicemicro-fluidic circuit in accordance with one embodiment of theinvention;

FIG. 4 is a schematic bottom view of a patient attachment unit of thefluid medicament delivery device of FIG. 1 with an external housingremoved;

FIG. 5 is a schematic perspective view of an indicator unit of the fluidmedicament delivery device of FIG. 1 with an external housing removed;

FIG. 6 is a schematic exploded perspective view of the indicator unit ofFIG. 5;

FIG. 7 is a schematic top view of the patient attachment unit of thefluid medicament delivery device of FIG. 1;

FIG. 8 is a schematic bottom perspective view of the indicator unit ofthe fluid medicament delivery device of FIG. 1;

FIGS. 9A-9D depict a procedure for mounting the indicator unit to thepatient attachment unit in accordance with one embodiment of the presentinvention;

FIG. 10 is a schematic section view of the fluid medicament deliverydevice of FIG. 1 taken along line 10-10;

FIG. 11 is a partial schematic section view of a well of FIG. 8 takenalong line 11-11;

FIG. 12 is a schematic section view of a fluid medicament deliverydevice in accordance with another embodiment of the present invention;

FIGS. 13A-13C depict a procedure for utilizing a fluid medicamentdelivery device in accordance with one embodiment of the presentinvention;

FIG. 14 is a system-level diagram of a fluid medicament delivery device;

FIG. 15 is a system-level diagram of an indicator unit;

FIG. 16 is a flowchart depicting a method for monitoring a fluidmedicament delivery device;

FIG. 17 is a flowchart depicting another embodiment of a method formonitoring a fluid medicament delivery device;

FIG. 18 is a flowchart depicting a method for measuring a fluidpressure:

FIG. 19 is a flowchart depicting a method for notifying a patient of atimer event;

FIG. 20 is a flowchart depicting a method for handing interrupts; and

FIG. 21 is a flowchart depicting a method for providing feedback to apatient.

DETAILED DESCRIPTION

FIGS. 1 and 2 depict an embodiment of an assembled fluid medicamentdelivery device 100 having at least tow modules, a patient attachmentunit 110 and a separate indicator unit 120, each having a housing 110 a,120 a, respectively. The depicted fluid medicament delivery device 100,when assembled, defines a substantially oval shape, although othershapes (circular, oblong, elliptical, etc.) are also contemplated. Ingeneral, an assembled device having round corners, smooth edges, etc.,may be desirable, since the device is designed to be worn on the skin ofa patient, underneath clothing. Other aspects of the device that make itgenerally unobtrusive during wear include a small size (only aboutseveral inches across) and a low profile. Other device shapes and sizesare also contemplated.

The patient attachment unit 110 includes a bolus button 268 fordelivering a dose of fluid medicament, as described below. A cannulainsertion device (See FIG. 13A) inserts a cannula through the device110, subcutaneously through the skin S of a patient. cannula insertiondevices are described in U.S. patent application Ser. No. 12/250,760,filed Oct. 14, 2008, the disclosure of which is hereby incorporated byreference herein in its entirety. After insertion, the cannula insertiondevice is disconnected from the patient attachment unit 110, and a cap112 is used to seal the opening to prevent ingress of contaminants,moisture, etc. The separate indicator unit 120 includes an indicatorbutton 122. A textured edge 124, may be present on all or part of theedge of the housing 120 a to provide a gripping surface duringattachment and/or disconnection of the indicator unit 120 and thepatient attachment unit 110, as described in more detail below.Alternatively or additionally, the edge of patient attachment unithousing 110 a may also be textured.

The patient attachment unit 110 is connected to and in communicationwith the separate indicator unit 120, as described in more detail below.The housings 110 a, 120 b of the patient attachment unit 110 and theindicator unit 120 meet at a curved interface 114. Interfaces havingother mating shapes are also contemplated. The bottom surface of thepatient attachment unit 110 includes a patient attachment interface 116.The patient attachment interface 116 may include one or more adhesivepads secured to the bottom surface of the patient attachment unit 110for adhering the fluid medicament delivery device 100 to the skin S of apatient during use. The interface 116 may comprise any suitableconfiguration to adhere the patient attachment unit 110 to the skin S.In one embodiment, the interface 116 includes a plurality of discretepoints of attachment. Other embodiments utilize concentric adhesivecircles or ovals.

the indicator button 122 may be used by the patient to test thefunctioning of the fluid medicament delivery device 100 or to cancel anotification presently being delivered or to prompt for a repetition ofa previous message or other information stored by the indicator unit.Actuating the indicator button 122 may initiate one or more tests toindicate to the patient various operational or therapy states of thedevice 100, such as whether the separate indicator unit 120 is properlymounted to the patient attachment unit 110, whether an internal batteryhas sufficient power for continued use, and/or whether pressure sensingwithin the device 110 is operating properly. Other tests are alsocontemplated. A single indicator button, such as that depicted in FIG.1, may be used to run one or more tests. The medicament delivery device100 may be programmed to recognize patterns of actuations of theindicator button to initiate certain test routines. That is, twoactuations in quick succession may initiate a “Battery Power Available”test routine, three actuations in quick succession may initiate a“Pressure Sensor Check” test routine, etc. Other combinations of shortactuations and long actuations (e.g., Short, Long, Short, Long, Long,Short, etc.) are also contemplated to initiate any number of testroutines. Alternatively or additionally, two or more buttons or otherinput features may be included on the device, for initiating one or moreseparate tests. Positive or negative feedback of the results may beprovided to the patient in the form of audible sounds of differing tonesor durations, illumination/delumination of lights, vibrations, andcombinations thereof. In certain embodiments, light emitting diodes(LEDs) may be used to illuminate the button itself or may illuminateportions of the indicator unit housing to provide feedback to thepatient. Graphical indicia or alphanumeric information may be displayedon a suitable output device.

FIG. 3 is a schematic diagram of an exemplary infusion devicemicro-fluidic circuit 250 that may be incorporated into the fluidmedicament delivery device 100 described herein. Other infusion deviceshaving micro-fluidic circuits are described in U.S. Patent ApplicationPublication No. 2005/0165384, published Jul. 28, 2005, the disclosure ofwhich is hereby incorporated by reference herein in its entirety. Themicro-fluidic circuit 250 includes a pressurized reservoir 252 that is,in this case, an elastomer bladder. Alternatively, a flexible vessel orbag compressed by a spring may be utilized. A fill port 254 is used tointroduce fluid, such as insulin, to the micro-fluidic circuit 250. Inthis micro-fluidic circuit 250, introducing insulin via the fill port254 fills both the reservoir 252 and a variable-volume bolus reservoir256. Check valves 258 prevent backflow of insulin in a number oflocations.

During use, insulin is forced from the reservoir 252 by elasticcontraction of the elastomer, through a filter 260, and into twoparallel flowpaths, a basal flowpath 262 and a bolus flowpath 264. Thebasal flowpath 262 delivers a constant dose or steady-state level ofinsulin to a patient; the bolus flowpath 264 delivers a bolus dose ofinsulin to the patient as needed or desired by the patient, for example,in conjunction with a meal. The basal flowpath 262 includes a firstpressure sensor 266A or other pressure or flow sensors in communicationwith the flowpath 262, for example, at a mid-point in the basalflowpath. In an alternative embodiment, the first pressure sensor 266Aor first sensing element 262 may be placed further upstream ordownstream in the basal flowpath, as desired. In another alternativeembodiment, a plurality of pressure sensors in communication with thebasal flowpath 262 may be utilized. A second pressure sensor 266B orsecond sensing element is exposed to ambient air pressure P. Thefunction of and relationship between the pressure sensors 266A, 266B isdescribed in more detail below. In one embodiment, the pressure sensors266A, 266B consist of micro-electronic-mechanical system (MEMS) sensors.Each MEMS sensor is about 2 mm square but sensors having differentdimensions may also be used. Both MEMS sensors are contained within theindicator unit 120. In FIG. 3, the pressure sensor 266A communicateswith a portion of the basal circuit 262 between two flow restrictors274A, 274B (e.g., microcapillaries). In one embodiment, this portionbetween the flow restrictors 274A, 274B may be a pressure sensorchamber, as described in more detail below. The pressure sensor 266Asenses pressure changes in the basal flowpath 262, which may beindicative of occlusion conditions that increase pressure therein. Thepressure sensor 266B senses changes in ambient air pressure external tothe fluid medicament delivery 100. The pressure sensors 266A, 266B areabsolute pressure sensors, but a single relative pressure sensor mayalso be utilized. A relative pressure sensor, e.g., a gauge MEMs sensor,may be used to replace both absolute pressure sensors.

To deliver a bolus via the bolus flowpath 264, the patient presses abutton 268 That drives a single stroke (delivering a single dose) of abolus displacement chamber 270 and opens two valves 272. The valves 272are in series for redundancy safety purposes. An optional flowrestrictor 274C regulates, in part, the fluid flow through the bolusflowpath 264. The parallel flowpaths 262, 264 join at a common channel276 just before an internal chamber or a cannula void 278. The cannulavoid 278 is formed in a cannula base 280, which allows a point ofconnection to a cannula 282. The cannula 282 extends below the skin S ofa patient, thus delivering the insulin subcutaneously. In oneembodiment, the actuation of the bolus button 268 may be sensed by theindicator unit 120 with, for example, a magnetic sensor, a Hall effectsensor, or a switch. In an alternative embodiment of the presentinvention, at least one pressure sensor may be placed in the bolusflowpath 264, thereby allowing the indicator unit 120 to sense theactuation of the bolus button 268. Conduits 284 having diameters largerthan those of the flow restrictors 274A, 274B, 274C connect the variouscomponents.

FIG. 4 depicts a bottom view of the patient attachment unit 110 showingthe internal components and structures therein, with the housingremoved. Specifically, the bottom portion of the housing 110 a, to whichthe attachment interface 116 is secured, has been removed. Theseinternal components and structures correspond generally to themicro-fluidic circuit 250, discussed in FIG. 3. The components andstructures in the patient attachment unit 110 may be disposed in orconnected to flow manifold 300, which serves as a mounting platform forthe various components. Note that not all conduits and flow componentsare depicted in FIG. 4, as some components may be secured to theopposite side of the manifold 300 or formed therein.

As described above with regard to FIG. 3, insulin in the bolus flowpath264 (the Bolus flowpath 264, in FIG. 4, is downstream of the labeledarrow) of the micro-fluidic circuit 250 is delivered from the elastomerreservoir 252, filtered through the filter 260, and stored in thevariable-volume bolus reservoir 256. In certain embodiment, theelastomer reservoir 252 may have a total volume of about 3200microliters; the variable-volume bolus reservoir 256 may have a totalvolume of about 180 microliters to about 260 microliters. Other volumesof the various components are also contemplated. When the fluid pressurein the elastomer reservoir 252 is greater than the fluid pressure in thevariable-volume reservoir 256, the variable-volume reservoir 256 willcontinue to fill, subject to the flow rate dictated at least by flowrestrictor 274C in the bolus flowpath 264. Downstream of thevariable-volume bolus reservoir 256 is the bolus displacement chamber270, which may store a single dose of insulin (e.g., about 5, about 10,about 20, or about 25, or greater than about 25 microliters of insulin,in various embodiments). A check valve 258 allows for free flow ofinsulin from the variable-volume bolus reservoir 256 to thebolus-displacement chamber 270. The check valve 258 prevents backflowduring a bolus stroke (i.e., actuation of the bolus button 268).

Actuating the bolus button 268 opens the two valves 272 (See FIG. 3) andempties the entire contents of the bolus displacement chamber 270.Audible, visual, and/or tactile feedback may be provided to the patientto signal that a bolus has been delivered. Releasing the bolus button268 closes the two downstream valves 272. The displacement chamber 270is then refilled with insulin from the variable-volume bolus reservoir256, which is in turn, filled with insulin from the reservoir 252. Thebolus flow rate is controlled with a fixed volume-per-stroke of bolusstimulus, i.e., a predetermined volume of insulin-per-stroke. In anotherembodiment, the bolus flow control rate also may be controlled by abolus rate flow restrictor. Also, downstream of the filter 260 is thebasal flowpath 262 (the basal flowpath 262, in FIG. 4, is downstream ofthe labeled arrow) of the micro-fluidic circuit 250. The flowrestrictors 274A, 274B are located on opposite sides of a pressuresensor chamber 302.

In various embodiments, each flow restrictor 274A, 274B has a length ina range of about 18 mm to about 35 mm. Other lengths of the flowrestrictors are also contemplated, for example, from about 10 mm toabout 20 mm. The various channels 284 in the manifold 300 may be formedby, for example, laser cutting, and the flow restrictors 274A, 274B maybe placed therein. The flow restrictors 274A, 274B may be glued or fusedinto the channels, though other methods of retention are alsocontemplated. Exemplary flow restrictors are described in U.S. patentApplication Publication No. 2006/0054230, the disclosure of which ishereby incorporated by reference herein in its entirety. The flowrestrictors 274A, 274B are connected to and in fluidic communicationwith a pressure sensor chamber 302 that includes a flexible member ofsensor membrane 302 a (See FIG. 7) disposed thereon. The sensor membrane302 a may be generally conterminous with a mating mounting platform 404(See FIG. 7) of the patient attachment unit 110, as described in moredetail below. As the insulin in the basal flowpath 262 flows into thechamber 302, pressure of the insulin within the basal flowpath 262displaces the sensor membrane 302 a. This displacement is sensed by thepressure sensor 266A, as described below. In this manner, the pressuresensor 266A may sense the pressure of the insulin in the basal flowpathvia movement of the sensor membrane 302 a.

FIG. 5 depicts a schematic perspective view of the indicator unit 120with the top exterior housing 120 a removed. FIG. 6 shows an explodedview of the indicator unit 120 depicted in FIG. 5. As discussed herein,the indicator unit 120 may, in certain embodiments, detect changes inpressure within the micro-fluidic circuit 250 contained in the patientattachment unit 110, and perform other test to ensure proper operationof the medicine delivery device 100. The patient may be alerted asnecessary via audible, visual, and/or tactile (e.g., vibration) signals.The components to detect pressure changes, process information, andgenerate signals or alerts to the patient are contained within theindicator unit 120.

The internal components of the separate indicator unit 120 are mounted,either directly or indirectly, to a mounting platform 350, which, in oneembodiment, may be the bottom surface of the indicator unit 120.Partially shown extending from the underside of the indicator unit 120is at least one circular mating projection 352, which is configured tomate with the patient attachment unit 110, as described below. Mountingarms 354 defining hollow interiors are disposed at or near the edges ofthe mounting platform 350. The mounting arms 354 correspond to andconnect to the top exterior housing 120 a with screw, snap-fit, press orother types of connections. Also disposed on the mounting platform 350are a supercapacitor 358, a vibrating motor 360, and two wells 362, 364.Each well 362, 364 defines a hollow geometrical structure, e.g., acylinder. Overlaid on at least the wells 362, 364 is a printed circuitboard (PCB) 366, which may include one or more processors, as well as atest switch 368 disposed thereon. Several apertures 370 formed in thePCB 366 correspond to and align with extensions 370 a from the mountingplatform 350. The extensions 370 a may be melted during manufacturing tosecure the PCB 366 thereto. The indicator button 122 aligns verticallyover the test switch 364. A piezoelectric sounder 374 or othersound-generating component is located proximate the PCB 366. One or morebattery holder solder pins 376 also penetrate the PCB. An activationswitch 378 interacts with an activation button 380, which contacts anactivation projection 428 (FIG. 7) on the patient attachment unit 110.

FIG. 7 depicts the patient attachment unit 110 and FIG. 8 depicts theunderside of the indicator unit 120. The elements that allow for theconnection and communication between both units 110, 120 are describedbelow. Indicator unit 120 has a contoured surface 400 that mates with amatching surface 402 of the patient attachment unit 110. The surfacesmay be of a undulating curved shape, as shown. Alternative embodimentsmay utilize crescent, linear, or other shaped surfaces. In anotherembodiment of the present invention, the contoured surface 400 of theindicator unit 120 may have a vertically-graded slope. The mating shapesof the leading surface 400 and the matching surface 402 assist inproperly securing and aligning the indicator unit 120 to the patientattachment unit 110 and help prevent inadvertent detachment of the twounits. Further, the complementary shapes of the contoured surface 400and the matching surface 402 direct the indicator units 120 to move inand out of a locking position, to connect and disconnect the indicatorunit 120 from the patient attachment unit 110 while ensuring properalignment of the operative components.

Proximate the matching surface 402 of the patient attachment unit 110 isa mating mounting platform 404. Multiple apertures 406, 408, and 410 inthe mounting platform 404 are configured to receive corresponding matingprojections 416, 414, 352 extending from a bottom surface 120 b of theindicator unit 120 to secure the two units. The apertures 406, 408, and410 may have a polygon, oblong, or other shape. Alternativeconfigurations, shapes, and orientations of the apertures 406, 408, 410and the mating projections 416, 414, 352 are contemplated. The wells362, 364 are formed in and are substantially coterminous with the bottomsurface 120 b of the indicator unit 120. In addition, a raised lip 412circumscribes the well 362 and projects above the bottom surface 120 b.The well 362 and the lip 412 are oriented to substantially align withthe sensor membrane 302 a when the patient attachment unit 110 andindicator unit 120 are connected. The sensor membrane 302 a issubstantially coterminous with the mating mounting platform 404, and isthe top surface of the pressure chamber 302, described above. A pressureequalizing membrane 426 also may be substantially coterminous with themating mounting platform 404. The function of the pressure equalizingmembrane 426 is described below. The activation projection 428 contactsthe activation button 380 when the patient attachment unit 110 isconnected to the indicator unit 120.

Each of the projections 416, 414, 352 of the indicator unit 120 matewith the corresponding apertures 406, 408, and 410 of the patientattachment unit 110 to form the complete assembled fluid medicamentdelivery device 100. Specifically, the guiding projection 416 mates withthe guiding aperture 406; the aligning projections 414 mate with thealigning apertures 408; and the circular mating projections 352 matewith the asymmetrically oblong apertures 410. Each mating pair hascorresponding shapes and corresponding orientations to secure theindicator unit 120 to the patient attachment unit 110. Each of thecircular mating projection 352 includes an enlarged end 352 a, which isenlarged relative to an extension 352 b that projects from the exposedbottom surface 120 b of the indicator unit 120. The enlarged end 352 ais configured and sized to fit within the enlarged portion 410 a ofaperture of aperture 410. When completely installed, as described below,the extension 352 b is partially surrounded by a constricted portion 410b of the oblong aperture 410.

The patient attachment unit 110 and the indicator unit 120 may besecured to and detached from one another as depicted in FIGS. 9A-9D.First, from the initial position depicted in FIG. 9A, the indicator unit120 is inverted (Step 1) such that the bottom surface 120 b is arrangedsubstantially opposite the mounting platform 404, as depicted in FIG.9B. The indicator unit 120 is then placed (Step 2) in close proximity tothe patient attachment unit 110, such that the enlarged ends 352 a ofthe circular mating projections 352 are aligned with and pass throughthe enlarged portions 410 a of the apertures 410. To completely securethe indicator unit 120 to the patient attachment unit 110, the patientslides (Step 3) the indicator unit 120 in an chordal direction, so thatthe extensions 352 b of the mating projections 352 are located withinthe constricted portion 410 b of the apertures 410. The enlarged ends352 a prevent the indicator unit 120 from being inadvertently dislodgedfrom the patient attachment unit 110. To disconnect the indicator unit120 from the patient attachment unit 110, the patient slides (Step 4)the indicator unit 120 in a direction opposite the direction of Step 3.Textured edge 124 may provide a gripping surface to facilitate thisstep. The enlarged ends 352 a are again aligned with the enlargedportions 410 a of the apertures 410, and the two units 110, 120 may beseparated.

The indicator unit 120 may be disconnected from the patient attachmentunit 110 in response to an occlusion event in the patent attachment unit110, or due to an electronics failure or low battery charge within theindicator unit 120. Additionally, the two units 110, 120 may bedisconnected because insulin in the patient attachment unit 110 may beexhausted or functionally depleted after prolonged use. In general, thismay occur after a period of time defined at least in part by the volumeof the elastomer reservoir 252 or the amount of insulin introduced tothe reservoir 252 during filling. In certain embodiments, the elastomerreservoir, when fully filled with insulin, may contain sufficientinsulin to dispense as needed for about 24, about 48, about 72, orgreater than about 72 hours. Other times are also contemplated, based onthe type of medicament being delivered, elastomer reservoir size,delivery schedule, etc. The separate indicator unit 120 alerts thepatient when insufficient levels of insulin remain in the patientattachment unit 110. When the insulin supply in the elastomer reservoir252 is exhausted or functionally depleted, the indicator unit 120 may bedisconnected from the patient attachment unit 110 and the patientattachment unit 110 may be disposed of. Another patient attachment unit110 may be obtained, filled with insulin and connected to the separateindicator unit 120, which may be re-used as long as it has sufficientbattery power. Alternatively, the exhausted or functionally depletedpatient attachment unit 110 may be refilled via the fill port 252.

Depicted in FIG. 10 is a cross-sectional view of the assembled fluidmedicament delivery device 100, depicting a number of internalcomponents, including the piezoelectric sounder 374, and the PCB 366,the battery 356, and the wells 362, 364. For clarify, many of thevarious conduits and components contained within the patient attachmentunit 110 are not depicted. This figure is used to show the generalmating relationship between the two units 110, 120. When the indicatorunit 120 is secured to the patient attachment unit 110, the bottomsurface 120 b of the indicator unit 120 is in close proximity butslightly spaced from the mounting platform 404, with the exception ofthe raised lip 412 of the well 362. The raised lip 412 of the well 362contacts the sensor membrane 302 a of the patient attachment unit 110.In alternative embodiments, other portions of the bottom surface 120 bmay contact the mounting platform 404. The pressure sensors 266A, 266Bare mounted to the PCB 366 and disposed in the wells 362, 364,respectively. Each well is filled with a substance to transmiteffectively pressure, for example, a solid resilient gel 362 a, 364 amanufactured of silicone gel, for example as manufactured by Dow CorningCorporation as product no. 3-4241. In general, silicone gels having ashore hardness of about 60 Shore 00 will produce satisfactory results.Other gels may also be utilized. During manufacture, to prevent leakageof the gel at the interface of the PCB 366 and wall of the wells 362,364, a portion of the gel 362 a is placed in each well 362, 364, andallowed to solidify. The remainder of the wells 362, 364 is thencompletely filled with the gel 362 a, which is in turn, allowed toharden. A meniscus 422 of the gel 362 a in the well 362 extends to theedge of the raised lip 412. Accordingly, when the patient attachmentunit 110 and the indicator unit 120 are connected, the meniscus 422 ofthe gel 362 a contacts the sensor membrane 302 a. The contact betweenthe gel 362 a and sensor membrane 302 a allows both to move in relationto one another. As fluid pressure increases within the pressure chamber302, the sensor membrane 302 a is forced against the meniscus 422. Thispressure is transmitted through the gel 362 a to the sensor 266A. In analternative manufacturing process, the wells 362 may be inverted andfilled from the underside, with the PCB 366 placed on the wells 362prior to curing of the gel.

Also shown in FIG. 10 is an ambient air channel 420, which is formedwhen the indicator unit 120 is attached to the patient attachment unit110. Since the mounting platform 404 and the bottom surface 120 b aregenerally not in contact, ambient air pressure may be transmitted freelyinto an interstitial space 420 a between the two units 110, 120. Thisexposes both a surface or meniscus 424 of the gel 364 a in the well 364and the pressure equalizing membrane 426 to ambient air pressure Pexternal to the device 100. This allows the device 100 to sense changesin ambient air pressure, as described below.

FIG. 11 depicts an enlarged inverted cross-sectional view of the well362. The pressure sensor 266A is mounted on the PCB 366 at the base ofthe well 362. As described above, the gel 362 a is filled to the edge ofthe raised lip 412. Three dashed lines 422A, 422B, and 422C illustratethe meniscus 422 of the gel 362 a according to various conditions. Line422A illustrates over-filling of the gel 362 a; line 422B illustratesdesired filling of the gel 362 a; line 422C illustrates under-filling ofthe gel 362 a. When the gel 362 a is filled to the desired level (i.e.,coplanar with the raised lip 412) the meniscus 422B is proximate withthe sensor membrane 302 a, while transferring little or no force betweenthe two elements. Force transmission remains minimal or nonexistentuntil fluid fills the pressure chamber 320. The raised lip 412 minimizesthe initial distance between the meniscus 422B and the sensor membrane302 a. If the gel 362 a has been over-filled, the meniscus 422A mayexert force on the sensor membrane 302 a, which may lead to inaccuratesensing. If the gel 362 a has been under-filled, the sensor membrane 302a may not contact the meniscus 422C, again leading to inaccuratesensing.

FIG. 12 depicts a simplified, schematic view of the fluid medicamentdelivery device 100 to illustrate the interrelationships between, aswell as the functionality of, the various components according to oneembodiment of the device 100. The patient attachment unit 110 includes asimplified, schematic version of the micro-fluidic circuit depicted inFIG. 3, contained within the housing 110 a. The flexible pressureequalizing membrane 426 is disposed within and substantially coterminouswith the mounting platform 404. The patient attachment unit 110 includesthe reservoir 252, for example, an elastomer bladder. The fill port 254may be used to introduce insulin into the reservoir 252. Insulindisplaced from the reservoir 252 fills the basal flowpath 262 and thebolus flowpath 264. Insulin flows through the bolus flowpath 264 andinto the patient via the cannula 282 when the bolus button 268 isactuated. Insulin in the basal flowpath 262 flows through the pressuresensor chamber 302, which includes a sensor membrane 302 a, which issubstantially coterminous with the top portion of the mounting platform404 of the patient attachment unit 110. Insulin from the basal flowpath262 and bolus flowpath 264 is introduced subcutaneously into the patientvia the cannula 282.

The simplified, schematic version of the indicator unit 120 includes thePCB 366, which is powered by the battery 352. The piezoelectric sounder374 and/or a light, such as a LED, is connected to the PC 366. Alsomounted on the PCB 366 are the pressure sensors 266A, 266B, which areeach disposed in the wells 362, 364, respectively. The well 364 depictedon the right in FIG. 12 includes the raised lip 412. Each well 362, 364is filled with the gel 362 a, 364 a, such that the meniscus 422, 424 isformed thereon.

When the indicator unit 120 is attached to the patient attachment unit110, the ambient air channel 420 and the interstitial space 420 a isformed therebetween. Note that the various connecting elements are notdepicted. Both the meniscus 424 of the gel 364 a and the flexiblepressure equalizing membrane 426 of the patient attachment unit 110 areexposed to the ambient pressure P_(A) in the interstitial space 420 a.

As insulin in the basal flowpath 262 flows through the pressure sensorchamber 302, when insulin pressure is greater than ambient pressure, theinsulin in the filled pressure sensor chamber 302 will flex the sensormembrane 302 a outwards. This outward deflection will, in turn, applypressure to the meniscus 422 of the gel 362 a, thus transmitting thatpressure to pressure sensor 266A. The PCB 366 interprets the pressureincrease and, if required, alerts the patient, e.g., via thepiezoelectric sounder 374 and/or the light.

Changes in pressure conditions in the basal flowpath that may occur forat least several reasons: (1) due to an occlusion or partial occlusiondownstream of the pressure sensor chamber 302; (2) due to an occlusionor partial occlusion upstream of the pressure sensor chamber 320; or (3)due to a pressure spike inherent in the last phase of contraction of theelastomer reservoir 252. An occlusion or partial occlusion causes thebasal flow to stop or partially stop. A pressure spike from theelastomer reservoir 252 occurs when the reservoir 252 is approaching thelimit of the reservoir's ability to continue the flow of insulin. Duringcontraction, the elastomer reservoir 252 maintains a substantiallyconstant pressure on the insulin delivered via the basal flowpath 262.However, as the reservoir 252 nears its fully contracted state, the wallapplies move force to the insulin, temporarily increasing the pressureuntil the wall achieves a final rest condition and the insulin pressureequalizes with that of the subcutaneous pressure of the patient. Thesepressure relationships are described in more detail below.

The indicator unit 120 may be programmed to conduct a pressure readingperiodically, for example, about every 30 minutes, to monitor thefunction of the fluid medicament delivery device 100. This allows forlow power consumption and provides for longer life of the battery 352.Periodic pressure readings allow the indicator unit 120 to alert thepatient to, and differentiate between, a change in fluid pressure causedby occlusions/partial occlusions and a change in fluid pressure causedby the last contraction phase of the elastomer reservoir 252. Asdescribed in more detail below, the electronic components containedwithin the indicator unit 120 may determine that a change in a pressureduring the early operational life of the device 100 is due to anocclusion (e.g., a blocked cannula 282). Further, the indicator unit 120may determine that a change in pressure during the late stages ofoperation of the device 100 is due to the last contraction phase of theelastomer reservoir 252. Regardless, upon detection of a pressure changeof a predetermined threshold valve, the patient will be alerted that thedevice 100 is not working properly and that the patient attachment unit110 needs to be replaced.

The fluid medicament delivery device 100 may operate properly in variousexternal pressure environments, for example, while a patient is atsea-level, at elevated pressure conditions (i.e., below sea-level), andat decreased pressure conditions (i.e., above sea-level). Additionally,due to the functionality described below, the components containedwithin the indicator unit 120 are able to distinguish pressure changescaused by occlusions from those caused by changes in ambient pressure.The fluid medicament delivery device 100 will continue operatingnormally in various external pressure environments and, thus, alert thepatient to changes in pressure that are only due to conditions thatrequire attention to the device 100 (e.g., an occlusion, a partialocclusion, or a near-empty condition of the elastomer bladder 252).

As described above, the indicator unit 120 includes two pressure sensors266A, 266B that are both absolute pressure sensors. When the indicatorunit 120 and patient attachment unit 110 are connected, the pressuresensor 266B is exposed to ambient air pressure P_(A), Table 1 depictsknown conditions for ambient pressure P_(A), subcutaneous (below theskin surface S) pressure P_(S) of a human body, and reservoir pressureP_(R). These pressures are given at sea-level, 1 meter below sea-level,and 3000 meters above sea-level. As an initial matter, due to thepresence of the pressure equalizing membrane 426, the ambient pressureP_(A) equals the device internal pressure P_(I). The human body is alsopressurized relative to the ambient air pressure P_(A). such that thesubcutaneous pressure P_(S) of the human body may be calculated as acombination of the ambient pressure and about 10 mbar. The reservoirpressure P_(R) exerted against the fluid contained therein may becalculated as the combination of the internal device pressure P_(I) andabout 820 mbar (i.e., the pressure exerted directly against the fluid bythe elastomer bladder material). The pressure exerted by the elastomerbladder material may be greater than or less than 820 mbar, depending onthe material used.

TABLE 1 Known Pressures for Use in Device Operation Ambient SubcutaneousPressure Pressure Reservoir Pressure All pressures in mbar P_(A) = P₁P_(S) = P_(A) + 10 P_(R) = P₁ + 820 Pressure at Sea-Level 1013 1023 1833Pressure at 1.0 meter 1113 1123 1933 submersion Pressure at 3000 800 8101620 meters altitude

Further, the fluid pressure P_(P) is sensed at pressure sensor 266Abecause the meniscus 422 of the gel 362 a contacts the sensor membrane302 a of the pressure sensor chamber 302 through which the insulinflows. Table 2 depicts fluid pressures P_(F) at sea-level, 1 meter belowsea-level, and 3000 meters above sea-level. Under Normal (i.e.,unblocked) conditions, the fluid pressure P_(F) at the pressure sensor266A is the average of the subcutaneous pressure P_(S) and the reservoirpressure P_(R). Table 2 also depicts fluid pressure P_(F) at completeocclusion and partial occlusion (so-called “half-blocking”) conditionsboth upstream and downstream of the pressure sensor chamber 302.Half-blocking conditions may occur when a flow channel or a flowrestrictor has a partial occlusion, allowing passage of inclusion atonly one-half of its rated flow rate.

TABLE 2 Fluid Pressures at Operational Conditions Upstream UpstreamDownstream Downstream All pressures Normal Occlusion Half-blockingOcclusion Half-blocking in mbar P₁ = (P_(S) + P_(R))/2 P₁ = P_(S) P₁ =(2 * P_(S) + P_(R))/3 P₁ = P_(R) P₁ = (P_(S) + 2 * P_(R))/3 Pressure at1428 1023 1293 1833 1563 Sea-Level Pressure at 1528 1123 1393 1933 16631.0 meter submersion Pressure at 1215 810 1080 1620 1350 3000 metersaltitude

Table 3 depicts pressure differentials ΔP at sea-level, 1 meter belowsea-level, and 3000 meters above sea-level. Generally, a Normal pressuredifferential ΔP may be about 450 mbar ±about 15%. In one embodiment, apressure differential ΔP between fluid pressure P_(F) and ambientpressure P_(A) from about 344 mbar to about 517 mbar at, below, or abovesea-level, is considered normal. A pressure differential ΔP below about344 mbar is considered a first failure state, generally caused by anupstream (of the pressure sensor chamber 302) occlusion, partialocclusion, or near-empty elastomer bladder condition. Apressure-differential ΔP above about 517 mbar is considered a secondfailure state, generally caused by a downstream (of the pressure sensorchamber 302) occlusion or partial occlusion. The uniform pressuredifferentials for each failure condition (i.e., upstream and downstreamocclusion, upstream and downstream half-blocking) allow the device todifferentiate between the various failure conditions. Informationregarding the various failure conditions may be stored in the componentswithin the indicator unit 120, for later download to a computer fordevice-diagnostic or other purposes.

TABLE 3 Pressure Differentials at Operational Conditions UpstreamUpstream Downstream Downstream All pressures Normal OcclusionHalf-blocking Occlusion Half-blocking in mbar ΔP = P_(F)-P_(A) ΔP =P_(F)-P_(A) ΔP = P_(F)-P_(A) ΔP = P_(F)-P_(A) ΔP = P_(F)-P_(A) Pressureat 415 10 280 820 550 Sea-Level Pressure at 415 10 280 820 550 1.0 metersubmersion Pressure at 415 10 280 820 550 3000 meters altitude

The pressure-equalizing membrane 426 allows the device to accuratelysense pressures and analyze the various pressure conditions duringoperation, either at, above, or below sea-level. Consider a proposedinsulin infusion device that lacks a pressure equalizing membrane(depicted as 426 in FIG. 12). Table 4 depicts known conditions forambient pressure P_(A), internal device pressure P_(I), subcutaneouspressure P_(S) of a human, and reservoir pressure P_(R). These pressuresare given at sea-level, 1 meter below sea-level, and 3000 meters abovesea-level. Since a pressure equalizing membrane is not utilized, theinternal device pressure P_(I) remains constant (in this case, at theenvironmental pressure at which the device was manufactured, e.g.,sea-level). In certain devices, the internal pressure P_(I) may beelevated, if the device was manufactured in a clean room, for example,which typically has a pressure higher than the ambient pressure of thelocation where the clean room is contained. Regardless, the constantinternal pressure P_(I) has a direct effect on the reservoir pressureP_(R), as shown in Table 4.

TABLE 4 Known Pressures for Use in Device Operation (NoPressure-Equalizing Membrane) Ambient Internal Subcutaneous ReservoirAll pressures in Pressure Pressure Pressure Pressure mbar P_(A) P₁ P_(S)= P_(A) + 10 P_(R) = P₁ + 820 Pressure at Sea- 1013 1013 1023 1833 LevelPressure at 1.0 1113 1013 1123 1833 meter submersion Pressure at 3000800 1013 810 1820 meters altitude

Table 5 depicts fluid pressures P_(F) at sea-level, 1 meter belowsea-level, and 3000 meters above sea-level, for a device lacking apressure-equalizing membrane. Fluid pressure P_(F) at complete occlusionand partial occlusion conditions upstream and downstream of the pressuresensor chamber 302 are also depicted in Table 5.

TABLE 5 Fluid Pressures at Operational Conditions (NoPressure-Equalizing Membrane) Upstream Upstream Downstream DownstreamAll pressures Normal Occlusion Half-blocking Occlusion Half-blocking inmbar P₁ = (P_(S) + P_(R))/2 P₁ = P_(S) P₁ = (2 * P_(S) + P_(R))/3 P₁ =P_(R) P₁ = (P_(S) + 2 * P_(R))/3 Pressure at 1428 1023 1293 1833 1563Sea-Level Pressure at 1478 1123 1360 1833 2395 1.0 meter submersionPressure at 1322 810 1151 1833 1492 3000 meters altitude

Table 6 depicts pressure differentials ΔP at sea-level, 1 meter belowsea-level, and 3000 meters above sea-level. As described above, a Normalpressure differential ΔP may be defined as about 450 mbar±about 15%.That is, a pressure differential ΔP from about 344 mbar to about 517mbar at, below, or above sea-level is considered normal. A pressuredifferential ΔP below about 344 mbar is considered a first failurestate; and pressure differential ΔP above about 517 mbar is considered asecond failure state. The pressure differentials depicted in Table 6show the advantages provided by a infusion device that includes apressure-equalizing membrane, such as that used with the devicedescribed herein. Absence of the pressure equalizing membrane may causeat least three types of problems. First, pressure differentials underNormal (i.e., unblocked) conditions may register as a failure condition(where a failure condition is defined as a pressure differential inexcess of 517 mbar). See, for example, the Normal condition pressure at3000 meters altitude, which is an operational altitude for an airplane.In such a case, the device is operating normally, but the deviceinterprets the pressure differential as a failure condition. The devicewould signal the patient that the device is not operating properly,which may cause the patient to remove and replace a device that isotherwise operating properly.

Second, a condition that should be interpreted as a failure conditionmay be overlooked. See, for example, the Upstream Half-blockingcondition pressure at 3000 meters altitude. There, the pressuredifferential fall within the normal range of about 344 mbar to 517 mbar.Thus, the device would not alert the patient to a failure conditions,even though there is blockage within the fluid circuit. This may cause aserious medical condition. Third, as can be seen, the pressuredifferential are not consistent across the same failure conditions,which would prevent the particular failure condition from beingsubsequently identified during diagnostics.

TABLE 6 Pressure Differentials at Operational Conditions (NoPressure-Equalizing Membrane) Upstream Upstream Downstream DownstreamAll pressures Normal Occlusion Half-blocking Occlusion Half-blocking inmbar ΔP = P_(F)-P_(A) ΔP = P_(F)-P_(A) ΔP = P_(F)-P_(A) ΔP = P_(F)-P_(A)ΔP = P_(F)-P_(A) Pressure at 415 10 280 820 550 Sea-Level Pressure at365 10 247 720 1282 1.0 meter submersion Pressure at  522* 10  351* 1033692 3000 meters altitude

FIG. 13A depicts a perspective view of a fluid medicament deliverydevice 100 in accordance with an embodiment of the invention. FIGS.13B-13C depict a procedure for using the fluid medicament deliverydevice 100. The fluid medicament delivery device 100 includes thepatient attachment unit 110 and the separate indicator unit 120. Ahousing for the cannula insertion device 450 and the bolus button 268are disposed on the patient attachment unit 110. An adhesive tape 452for adhering the device 100 to the skin of a patient is disposed on theunderside of the patient attachment unit 110. A liner 454 is included tocover the adhesive tape 452 before the device 100 is attached to thepatient.

The device 100 is first removed its packaging (Step 500) which keeps thedevice 100 clean during storage and transport, prior to use. Theseparate indicator unit 120 is mounted to the patient attachment unit100 (Step 502), for example, in the manner described above and shown inFIGS. 9A-9C. To fill the device 100 with the insulin (Step 504), aninsulin pen 254 a is connected to a fill port 254 on the underside ofthe patient attachment unit 110. Insulin is then dispensed from the pen254 a to fill the insulin reservoir (Step 506). Once full, the insulinpen 254 a is disconnected from the device 100 and discarded (Step 508).The liner 454 is then removed from the device 100 to expose the adhesivetape (Step 510). The patient attachment unit 100 is then adhered to anappropriate portion of the patient's skin S (Step 512). Acceptablelocations include, but are not limited to, the abdominal area, the areaabove the buttocks, or the area proximate the triceps muscle. Thepatient then actuates the cannula insertion device 450 to insert thecannula into the body (Step 514). The patient disconnects the housing ofthe cannula insertion device 450 from the patient attachment unit 110(Step 516). The device 100 is now operational and may be worn by thepatient during normal, everyday activities. When the device 100 needs tobe removed (either due to a failure state or depletion of insulin), thepatient peels the device 100 from the skin S (Step 518). As shown inStep 520, the patient may then detach the indicator unit 120 from thepatient attachment unit 110, as described above with regard to FIG. 9D.The indicator unit 120 may then be attached to a new patient attachmentunit 110. In this way, the comparatively more-expensive indicator unit120 may be reused, while the less-expensive patient attachment unit 110may be disposed of.

The various components utilized in the device described herein may bemetal, glass, and/or any type of polymer suitable for sterilization anduseful for delivering insulin or other medicaments subcutaneously.Polyurethane, polypropylene, PVC, PVDC, EVA, and others, arecontemplated for use, as are stainless steel and other medical-grademetals. More specifically, medical-grade plastics may be utilized forthe cannula itself, as well as other components that contact orotherwise penetrate the body of the patient. Needless and springs madefrom medical-grade stainless steel are also desirable, to preventfailure associated with use.

FIG. 14 is a block diagram illustrating one embodiment of a fluidmedicament delivery device 1400. The device 1400 may include some or allof the features and components of the embodiments of the devicesdescribed above, such as the fluid medicament delivery device 100, evenif they are not explicitly shown in FIG. 14. Aspects of the fluidmedicament delivery device 1400 may be hereinafter described asconceptual blocks or modules, that may encompass some or all of thecomponents described herein. It will be understood by a person ofordinary skill in the art that the illustrated modules may beconceptual, rather than explicit, requirements. For example, two or moremodules may be combined into a single module, such that the functionsperformed by the two or more modules are, in fact, performed by thesingle module. In addition, it will be understood that any single one ofthe modules may be implemented as multiple modules, such that thefunctions performed by any single one of the modules are, in fact,performed by the multiple modules. Moereover, the fluid medicamentdelivery device 1400 may be modified in a variety of manners withoutdeparting from the spirit and scope of embodiments of the invention. Assuch, the depiction of the fluid medicament delivery device 1400 in FIG.14 and in other figures is non-limiting.

The fluid medicament delivery device 1400 includes a patient attachmentunit 1402 and an indictor unit 1404. The patient attachment unit 1402includes a fluid reservoir 1406 and a pressure sensor chamber 1408. Thefluid reservoir 1406 may include one or more reservoirs. Fluid from thefluid reservoir 1406 passes through the device 1400 via a first path1412 (e.g., a basal flow path) through the pressure-sensor chamber 1408and a second path 1414 (e.g., a bolus flow path). A cannula 1410 allowsfor delivery of the fluid to a patient.

The indicator unit 1404 includes, in one embodiment, a sensor 1416, aninterrupt handler 1418, a sensing module 1420, a notification module1422, an initialization module 1424, and a status determination module1426. The sensor 1416 may be, for example, the first pressure sensor266A and/or the second pressure sensor 266B described above, and maysense a pressure of the fluid in the pressure sensor chamber 1408 and/oran ambient air pressure.

FIG. 15 depicts one embodiment of the indicator unit 1404. A centralprocessing unit (CPU) 1502 is programmed to perform the operationsdescribed above, such as conducting a pressure measurement, and otheroperations described further below. The CPU 1502 may include aprocessor, memory, storage device, and/or other components typicallyused in a low-power, embedded CPU, as understood by one of ordinaryskill in the art. The CPU 1502 communicates with an analog-to-digital(A/D) pressure input 1504, an digital input/output (“I/O”) interface1506, and actuation devices such as an activation switch 1508 and a testbutton 1510.

The CPU 1502 may include a main process 1512 that performs measurementand logic analysis and coordinates information with other CPU modules. Atimer 1514 my track the passage of time and enable CPU operations tooccur at certain times or time intervals. In one embodiment, the timer1514 is a sample timer and triggers a sample interrupt for initiating asensor measurement. The sample timer may be configured to expire aboutevery 30 minutes, trigger an interrupt, and reset and count again fromzero. In another embodiment, the timer 1514 includes a cycle counterthat tracks the number of times the sample timer has expired. The timer1514 may be capable of counting larger durations of time, for example,up to the 72-hour time limit of use of a patient attachment unitdescribed herein. Other longer and shorter sample time limits arecontemplated.

The CPU 1502 may include a non-volatile memory 1516 for storing data.The contents of the non-volatile memory may be preserved, even if theindicator unit is turned off and/or loses battery power. In oneembodiment, the CPU 1502 stores forensic data in the non-volatile memory1516. Similarly, the CPU 1502 may store the results of prior pressuremeasurements in a lookback pressure buffer 1518, which may includevolatile or non-volatile memory. The lookback pressure buffer 1518 maybe sized to store the history of every pressure measurement taken for apatient attachment unit life cycle, or may be limited in size and deleteolder pressure data to accommodate new data.

The CPU 1502 may also include an interrupt handler 1520 for capturingexternal events, such as the actuation of the activation switch 1508 andthe test button 1510, and for generating an interrupt in response. Theinterrupt handler 1520 may also detect the expiration of the timer 1514and generate an appropriate interrupt.

The CPU 1502 may also communicate with other input devices, such as afluid pressure sensor 1522, an ambient pressure sensor 1524, a bolusbutton sensor, and/or other output devices, such as patient signals 1526(including a vibrator 1526 a, LEDs 1526 b, and/or a sounder 1526 c).Signals 1522 a, 1524 a generated by the sensors 1522, 1524 may be analogsignals and are, therefore, converted to digital signals with the A/Dconverter 1504 before the CPU 1502 receives them. Due to the high powerrequirements of the sensors 1522, 1524, the device 1404 may utilize asensor bias power unit 1532, which may bias the sensors 1522, 1524 at anappropriate voltage only when a measurement is to be taken, therebyreducing the overall power consumption of the indicator unit 1404.Alternatively, the sensor bias power unit 1532 may be eliminated and thesensors 1522 and 1524 may be powered on a continuous basis. In certainembodiments of the device where battery size is a consideration, thisconfiguration may be less desirable. The CPU 1502 may drive the patientsignals 1526 directly or indirectly, using the digital I/O interface1506. A battery may provide power to the CPU 1502 and other modules.

FIG. 16 depicts a method 1600 for monitoring a fluid medicament deliverydevice. In brief, the method 1600 begins by conducting a systeminitialization test (Step 1602). Next, a sensing mode is initiated uponreceipt of an interrupt request (Step 1604). The flow rate of a fluid iscontrolled with a patient attachment unit (Step 1606). A parameter ofinterest of a fluid, such as a flow rate or a fluid pressure, and/or theambient air pressure is measured (Step 1608). The status of a fluidmedicament delivery device is determined (Step 1610), and a patient isnotified of the status (Step 1612), if required. Finally, the interruptrequest, fluid-pressure, flow rate, ambient air pressure, and/or statusmay be stored in a non-volatile memory (Step 1614).

FIG. 17 shows another embodiment of a method 1700 for monitoring a fluidflow with an indicator unit. The method begins by activating theindicator unit (Step 1702). The activation may occur, for example, whenthe indicator unit is coupled to the patient attachment unit, as aresult of a patient-activated button or switch, and/or during producttesting. An initialization test is performed (Step 1704), in which theindicator unit may perform hardware integrity diagnostics on itscircuitry and electronic components (e.g., perform a test on wirebonding pads for open or short circuits). If the initialization/hardwareintegrity test fails, the method 1700 may lock-out the indicator unit toprevent further use (Step 1710) and send a communication to the patientindicative of the lock-out condition, thereby advising the patient toreplace the indicator unit. If the initialization/hardware integritytest succeeds, the method 1700 next determines the level of powerremaining in a battery (or batteries) providing power to the indicatorunit (Step 1706). If the battery power is too low to power reliably theindicator unit for at least one more treatment cycle, the indicator unitis locked out (Step 1710). If, on the other hand, there is sufficientbattery power for at least one more treatment cycle, the patient isnotified if the battery power is usable but low (Step 1708), and themethod 1700 continues.

If the initialization test (Step 1704) and the battery power test (Step1706) have positive outcomes, the indicator unit updates the forensicinformation stored on the device (Step 1714). In one embodiment, theforensic information is stored in a non-volatile memory. Examples offorensic information to be stored include one or more of the following:the results of current or previous pressure measurements; the ambientpressure, fluid pressure, and/or battery voltage at time of activationand/or initialization; the interval number, time, and/or cycle in whicha product alert was generated; the number of times a warning buzzer wasactivated; the number of signals triggered due to a low-batterycondition; the number of alerts triggered due to a blocked fluid flow, alow-fluid condition, and/or the exceeding of a time limit; the number ofelapsed treatment cycles; the number of times a test button was pressed;and/or other information. In one embodiment, some or all of olderforensic information is overwritten by new information; in anotherembodiment, old and new forensic information are maintained separatelyor combined to create summary information.

In one embodiment, the indicator unit enters a sleep state (Step 1712)before adapting forensic information (Step 1714) and remains in thesleep state until an external event occurs, such as the interrupttriggering of the sample timer. The sleep state may also be entered oncethe monitoring process 1700 completes. The sample timer may beconfigured to send out a trigger notification at periodic intervals,such as, for example, every 10, 15, 20, 30, or 60 minutes or more. Inone embodiment, the indicator unit enters a low-power mode while in thesleep state (i.e., between sample timer trigger events), and exits thelow-power mode upon leaving the sleep state.

Next, one or more measurement sensors are read and the results areanalyzed (Step 1716), as discussed with regard to FIG. 18. Once themeasurement results are obtained, an action is taken based on the lengthof time the indicator unit has been active (Step 1718), as discussedwith regard to FIG. 19. Thereafter, the CPU may prepare the indicatorunit for the next sample cycle (Step 1720). In one embodiment, the CPUsets an interrupt for the sample timer, thereby initiating its nextcounting cycle. The CPU may also bring the indicator unit into alow-power mode. The sample cycle then ends (Step 1722).

FIG. 18 depict one embodiment of a subroutine for reading themeasurement sensors and analyzing the results (Step 1716) of the method1700 of FIG. 17. First, a measurement signal produced by a sensor isread and, if necessary, processed to remove undesirable noise (i.e.,“debounced”) (Step 1802). In one embodiment, the sensor is a fluidpressure sensor and the measurement signal indicates the pressure of amedicament fluid. In another embodiment, an ambient air pressure sensoris also read to determine the ambient air pressure. If both the fluidpressure and the ambient air pressure are sensed, the difference betweenthe pressures may be computed (Step 1804). Comparing the fluid pressureto the ambient pressure may improve the quality of the measurementresults, because doing so may, for example, reduce inconsistencies inpressure reading caused by changes in altitude, as described above. Themethods described herein equally apply to measurements of the fluidpressure alone.

A measurement result—which may be the fluid pressure or the differencebetween the fluid and ambient pressures—is analyzed to determine if itis a valid and usable measurement (Step 1806). An invalid and/orunusable measurement or “bad value” may occur because of a permanentcondition, such as a hardware error in one or more of the sensors, orbecause of temporary condition, such as a correctly-sensed by invalidfluid pressure caused by, for example, an extreme movement of thepatient and/or intense radio-frequency interference.

If a bad value is detected, previous measurements may be analyzed andcompared to the current bad value to determine the nature of the badvalue (Step 1808). If another had value had recently occurred, themethod may determine that the cause of the bad value is legitimate andpermanent (i.e., and occlusion of the fluid flow path or a hardwarefault), and accordingly notify the patient of the occlusion/faultcondition (Step 1812). Alternatively, the device may also differentiatebetween a complete occlusion, a partial occlusion, or hardware faultcondition and notify the patient accordingly. In one embodiment, thecause of the bad value, such as a fluid flow problem or a sensormalfunction, is also communicated to the patient. If, however, a usablemeasurement occurred in a recent prior measurement, the cause of thecurrent bad value may be result of temporary condition. Accordingly, themeasurement process exits (Step 1810) and the process is retried at thenext sample timer interrupt.

If the measurement result is determined to be usable, the value of themeasurement is analyzed (Steps 1814, 1816) to determine if themeasurement result deviates more than a predetermined amount from atypical result. In one embodiment, the measurement result is analyzedfor a deviation of 50% less than a typical value (Step 1814) or 50%greater than a typical value (Step 1816). If the measurement resultdeviates from the typical result by more than the predetermined amount,prior measurement results may be analyzed to determine if the amount ofthe deviation had been stable for more than a certain amount of time(such as, for example, 30 minutes) (Steps 1818, 1820). If so, thepatient is alerted of an occlusion condition (Step 1812). The increaseor decrease in pressure may be the result of an occlusion downstream orupstream from the pressure sensor, respectively.

An exception in the deviation measurement may be made during the initialstartup time of the indicator unit (Step 1822). During the initialstartup time (e.g., about 30 to about 60 minutes after filling of thereservoir, in one embodiment), the value of the measurement may be lessthan typical because, for example, the fluid pressure in the pressuresensor chamber has not yet reached its typical operating pressure. Alow-pressure measurement during the initial startup time may thereforebe typical of the start-up process, and the method may delay alertingthe patient until after the initial startup time has elapsed. One theinitial startup time has elapsed, if the error persists, the patient maythen be notified.

In one embodiment, the fluid pressure in the patient attachment unit isevaluated for a sign of early depletion (Step 1824). Under normal usage,the fluid reservoir in the patient attachment unit contains a supply offluid medicament sufficient to last for at least the unit's expectedduration of use (e.g., about 72 hours). In some circumstances, though,the fluid supply may be insufficient to last for the full duration, forexample where the patient uses an unexpectedly large number of bolusdoses, and the indicator unit may determine that the fluid is nearingthe end of its supply. In one embodiment, a low fluid condition isdetermined by detecting the presence of a pressure spike resulting fromthe last phase of contraction of an elastomer fluid reservoir. If thispressure spike is detected and distinguished from an occlusioncondition, the indicator unit may advance the timer ahead to the maximumexpected use time (e.g., 72 hours) (Step 1826), thereby triggering, inlater steps, a patient alert signaling the dwindling fluid supply. Ifthe sensor measurement is later run again, and a pressure spike is againdetected, the previously-advanced timer value is not disturbed. In oneembodiment, the peak pressure of the pressure spike is about 15% toabout 20% greater than a typical baseline steady state pressure in thebasal circuit. Other peak pressures may also be considered. For example,a typical pressure of the fluid may be 400 bar. During the initialstartup time, the fluid pressure starts at 0 bar and increases to 400bar, though no low-pressure alert is generated. Once the initial startuptime has elapsed, if the pressure is less than 200 bar or greater than600 bar, the occlusion test steps 1814, 1816 detect an occlusioncondition. If there is a pressure spike of approximately 460-480 bar,the early depletion step 1824 detects a low fluid condition.

Before the sensor measurement completes, one or more items ofinformation determined during the course of the sensor measurement (Step1828) may be stored in the non-volatile memory, as described above. Inone embodiment, the information is stored in a non-volatile forensicbuffer. In another embodiment, one or both of the pressures determinedin the measurement step are stored in a lookback pressure buffer,thereby preserving the pressure(s) for use in, for example, futuresensor measurement comparisons to evaluate data trends or for otherpurposes.

FIG. 19 depicts one embodiment of a subroutine for reading the timer andtaking an appropriate action (Step 1718) of the method 1700 of FIG. 17.In this subroutine, the value of the timer may be compared against oneor more threshold times, and the patient is alerted if a threshold hasbeen reached. For example, the value of the timer is compared against anearly change notification time (e.g., 48 hours) (Step 1902). If theearly change notification time has elapsed, a notification is sent towarn the patient that the patient attachment unit may soon requirereplacement (Step 1904). In one embodiment, if the patient presses atest button before the early change notification time has elapsed, theindicator unit sends either no response or a response indicating thatthe unit is operating normally. If, however, the patient presses thetest button after the early change notification time has elapsed, theindicator unit may send a warning signal, such as a vibration, to informthe patient that the patient attachment unit may soon requirereplacement.

The timer value is also compared to the maximum expected time of use(e.g., about 72 hours) (Step 1906). If the timer exceeds the maximumexpected time of use, a “Replace” notification is sent to the patient(Step 1908) instructing the patient to replace the patient attachmentunit. In one embodiment, further “Replace” notification are sent to thepatient at later intervals of time, for example, at about 72.5 hours,about 73 hours, and at about 73.5 hours, urging replacement of thepatient attachment unit. The “Replace” notification can be more urgent(e.g., louder, stronger, longer, etc.) as additional time elapses.

Once the value of the timer passes a second threshold (Step 1910),however, an out-of-fluid alert is sent to the patient (Step 1912). Thesecond threshold may be a predetermined time at which the fluidreservoir will run out of fluid. In one embodiment, the out-of-fluidalert is repeatedly sent to the patient, for example, every thirtyminutes.

After each notification and/or alert is sent to the patient, relevantforensic information may be recorded (Step 1914). The forensicinformation may include the type of timer action triggered, the type ofalert sent, the number of times the bolus button is pressed and/or thetotal number of actions and alerts. Patient acknowledgement of receiptof an alert and/or notification by, for example, pressing a responsebutton, may also be recorded.

The indicator unit may interact with external event, such as switchtoggles, button presses, and timer events, by means of an interrupthandler. A flow chart illustrating one embodiment of an interrupthandler process 2000 is shown in FIG. 20. Proceeding from an interruptevent (Step 2002), the interrupt handler process 200 illustrates thehandling of three categories of events—a switch event (Step 2004), abutton event (Step 2006), and a timer event (Step 2008)—but other,similar categories of events are contemplated and within the scope ofthe invention.

The switch event (Step 2204) detects a change in the state of anactivation switch on the indicator unit. The signal generated by theactivation switch is debounced (Steps 2010, 2012), wherein the signal ismonitored for consistency over N seconds until a clean change in thestate of the activation switch is detected. The new state of theactivation switch is evaluated (Step 2014). If the new state isactivated or “on,” the indicator unit may be powered on (Step 2016) by,for example, transferring control to the first step of the main loop1700, starting at step 1702, as depicted in FIG. 17. In one embodiment,certain interrupts are masked to prevent the indicator unit from wakingup when certain events occur (Step 2020). For example, in sleep mode,the indicator unit may ignore presses of a test button, but may wake upfront sleep mode when the activation switch toggles. Forensicinformation (such as the time of entry into the sleep mode, thecalculated fluid reservoir capacity, number of times a bolus button waspressed, and/or the battery power available) may be written to thenon-volatile memory (step 2020). If the new state is deactivated or“off,” the indicator unit may be placed into a power-conserving “deepsleep” mode (Step 2018), to conserve battery power. This mode may beuseful for shipment or storage of the patient attachment unit.

The indicator unit may include a test or “indicator” button permitting apatient to check the status of the unit upon actuation. Additionally,the indicator button may be used to silence a notification currentlybeing delivered. An interrupt created by the actuation of the button isdetected (Step 2006) and the last notification and/or alert sent to thepatient is determined (by, for example, reading past forensicinformation from the non-volatile memory) and re-sent (step 2022). Inone embodiment, the indicator unit performs a new pressure measurementin response to the pressing of the test button, and sends a notificationbased on the new measurement. The sending of the repeated notificationand/or the new test result may be saved to the non-volatile memory (Step2024). In other embodiments, different patterns of test button pressesare detected and produce different types of interrupts. The indicatorunit may include additional buttons to perform different functions.

The expiration of the sample timer, which may occur at regularintervals, about every 5, 10, 15, 20, 25, or 30 minutes, for example,may trigger a timer event (Step 2008). At each sample timer event, acycle counter may be incremented (Step 2026), and the main sample loop1700 (depicted in FIG. 17) may be launched (Step 2028), starting at Step1712. The interrupt handler routine ends regardless of the type ofinterrupt (Step 2030) and enters a sleep state awaiting the nextinterrupt.

At each expiration of the sample timer, the total time of use of theindicator unit may be determined by multiplying the current cyclecounter value by the sample time expiration value. For example, if thesample timer expires every 30 minutes and the value of the cycle counteris ten, the total time of use is 300 minutes or 5 hours, the product ofthe sample time period and the number of cycles. Thus, steps thatrequire the total time of use, for example, timer Steps 1902, 1906, maydetermine the total time of use from the sample rate and cycle counter.

FIG. 21 depicts one embodiment of a method 2100 for determining the typeof Patient notification required. Different types of notifications oralerts may be communicated to the patient by different means, dependingon the type and/or urgency of the notification or alert. The medicinedelivery device described herein generally utilized discreetnotifications to alert a patient to particular conditions, withoutunnecessarily alerting nearby persons to the patient's use of thedevice. For example, an alert of notification may trigger a tactilemessage (i.e., a vibration) at first but, if the patient fails torespond to or is unable to detect the tactile message, the type ofnotifications or alert may escalate to more observable types (e.g.,sound, lights, etc.) alone or in combination. Frequency and magnitude ofnotification or alert can also be escalated. The process starts (Step2102) and evaluates the source of the patient notification request (Step2104). Less urgent notifications or alerts may require only a briefnotification, while more urgent notifications or alerts may require moreextensive notifications. The notifications or alerts may vary in type(e.g., light-based for minor events, sound-based for intermediateevents, and vibration-based for important events) and degree (e.g.,brighter or dimmer lights, different colors of lights, louder or softersounds, and/or stronger or weaker vibrations). For example, the patientmay be notified of a successful pressure test with a green light and ofa low-fluid condition with vibration. In one embodiment, two or moretypes of alerts are combined in the same notification. The patient mayspecify a preferred type of notification (e.g., vibration-based forhearing-impaired patients or sound-based for visually-impairedpatients).

Once the type of notification is assessed (Step 2104), the notificationrequirements are evaluated to determine if vibration, sound and/or lightis required (Steps 2106, 2108, 2110). The CPU produces the correspondingvibration, sound, and/or light notifications in response (Steps 2112,2114, 2116). A discretion delay may be inserted between a first discreetnotification and a second over notification (Step 2118) to allow thepatient to cancel the notification or alert once the discreetnotification is received. In one embodiment, a tactile message (e.g., avibration) is first sent and the patient is given a ten-second window tocancel the notification by, for example, pressing the test button (Step2120 a). If the test button is pressed, the patient thereby acknowledgesreceipt of the notification and no further notifications are sent. If,however, the patient does not press the test button, the notificationmay escalate to sound and/or light-based messages. In anotherembodiment, a light-based message is sent first, and a tactile- and/orsound-based message is sent after a delay. The patient notification maybe cancelled during escalated notifications (Steps 2120 b, 2120 c), aswell as during the first, discreet notification (Step 2120 a).

In one embodiment, the patient notification conveys informationregarding the notification type. For example, a green light may signifyan “OK” state, a yellow light a “warning” state, and a red light an“error” state. In one embodiment, a sound-based notification includestwo or more tones. The tones may be arranged, for example, at a highpitch, with an increasing or rising frequency, and/or in accordance witha major scale to convey an “OK” state. On the other hand, the tones maybe arranged at a low pitch, with decreasing frequency, and/or inaccordance with a minor scale to convey a warning or error state. Tonesor sounds may include those generally recognized by a human as havingpositive or negative associations. The patient notification process endswhen the appropriate notifications have been sent (Step 2122).

While there have been described herein what are to be consideredexemplary and preferred embodiments of the present invention, othermodifications of the invention will become apparent to those skilled inthe art from the teachings herein without departing from the spirit oressential characteristics thereof. The present embodiments are thereforeto be considered in all respects as illustrative and not restrictive.The particular methods of manufacture, geometries, and methods ofoperation disclosed herein are exemplary in nature and are not to beconsidered limiting. It is therefore desired to be secured in theappended claims all such modifications as fall within the spirit andscope of the invention. Accordingly, what is desired to be secured byLetters Patent is the invention as defined and differential in thefollowing claims, and all equivalents.

What is claimed is: 1-30. (canceled)
 31. A system for monitoring a fluidmedicament delivery device, the system comprising: a patient attachmentunit comprising a pressure sensor chamber disposed along a basal flowpath, wherein the pressure sensor chamber comprises a sensor membrane;and an indicator unit configured to be detachably coupled to the patientattachment unit, wherein the indicator unit comprises a pressure sensorin communication with the pressure sensor chamber.
 32. The system ofclaim 31, wherein the indicator unit further comprises a well in whichthe pressure sensor is disposed.
 33. The system of claim 32, wherein thewell comprises a raised lip.
 34. The system of claim 33, wherein theraised lip is configured to abut a mounting platform of the patientattachment unit.
 35. The system of claim 32, wherein the well is filledwith a gel to form a meniscus.
 36. The system of claim 35, wherein themeniscus and the sensor membrane abut each other.
 37. The system ofclaim 36, wherein deflections in the sensor membrane are configured toapply pressure to the meniscus of the gel, which transmits the pressureto the pressure sensor.
 38. The system of claim 31, further comprisingan ambient air channel formed between the patient attachment unit andthe indicator unit.
 39. The system of claim 38, further comprising aflexible pressure equalizing membrane disposed in the patient attachmentunit, wherein the flexible pressure equalizing membrane is incommunication with the ambient air channel.
 40. The system of claim 38,further comprising a second pressure sensor disposed within theindicator unit.
 41. The system of claim 40, wherein the indicator unitfurther comprises a second well in which the second pressure sensor isdisposed.
 42. The system of claim 41, wherein the second well is filledwith a gel to form a meniscus, which is in communication with theambient air channel.
 43. A system for monitoring a fluid medicamentdelivery device, the system comprising: a patient attachment unitcomprising a mounting platform and a pressure sensor chamber disposedalong a basal flow path, wherein the pressure sensor chamber comprises asensor membrane; and an indicator unit configured to be detachablycoupled to the patient attachment unit, wherein the indicator unitcomprises a pressure sensor disposed in a well having a raised lip,wherein the pressure sensor is in communication with the pressure sensorchamber, wherein the raised lip is configured to abut the mountingplatform to form an ambient air channel between the patient attachmentunit and the indicator unit.
 44. The system of claim 43, wherein thewell is filled with a gel to form a meniscus.
 45. The system of claim44, wherein the meniscus and the sensor membrane abut each other. 46.The system of claim 45, wherein deflections in the sensor membrane areconfigured to apply pressure to the meniscus of the gel, which transmitsthe pressure to the pressure sensor.
 47. The system of claim 43, furthercomprising a flexible pressure equalizing membrane disposed in thepatient attachment unit, wherein the flexible pressure equalizingmembrane is in communication with the ambient air channel.
 48. Thesystem of claim 43, further comprising a second pressure sensor disposedwithin the indicator unit.
 49. The system of claim 48, wherein theindicator unit further comprises a second well in which the secondpressure sensor is disposed, wherein the second well is filled with agel to form a meniscus that is in communication with the ambient airchannel.
 50. A method for monitoring a fluid medicament delivery device,the method comprising: providing a patient attachment unit comprising apressure sensor chamber disposed along a basal flow path; providing anindicator unit configured to be detachably coupled to the patientattachment unit, wherein the indicator unit comprises a pressure sensorin communication with the pressure sensor chamber; and determining apressure condition in the basal flow path.